Fire detection system



July 2, 1968 v. v. SMITH 3,391,401

FIRE DETECTION SYSTEM Filed Nov. 10, 1965 TIE, ,2 W...-

j rralws United States Patent 3,391,401 FIRE DETECTION SYSTEM Voyle V. Smith, 301 Bexar Drive, San Antonio, Tex. 78228 Filed Nov. 10, 1965, Ser. No. 507,258 4 Claims. (Cl. 340227.1)

The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to a temperature sensing device and more particularly is concerned with providing a fire detection system for sensing the existence and indicating the location of a fire or excessive heat in some remote area such as in an aircraft engine or storage area.

Although fire detection systems are presently in use for sensing the existence of fires especially on aircraft, they are not fully satisfactory because of the use of unduly complicated mechanisms which reduces their dependability under adverse operating conditions. Also, most presently known systems are complex and include extensive installation and maintenance requirements. The present invention is directed to a relatively simple mechanically activated detection system which is extremely dependable and easily installed and maintained. It provides means for detecting the presence and location of a fire in an area remote from the observer and also indicates if and when the fire is extinguished.

Accordingly, it is an object of the present invention to provide a fire detection system which is mechanically simple and easily maintained and which is capable of indicating the existence and location of a fire, especially in an aircraft.

Another object of the invention is to provide a fire detection system having a remotely disposed actuating mechanism which is responsive to rapid ambient temperature changes in the installation area and provides an actuating means for energizing a signal which indicates the conditions in the remote area.

Still another object of the invention is to provide a fire detection system which utilizes a thermal sensing element having a bimetal strip which responds to rapid ambient temperature changes in the zone in which the sensing element is located.

A further object of the invention is to provide a fire detection system having a plurality of detecting elements located in various remote areas in the structure being protected. The location of each of the detecting elements is predetermined so that any signal received from the sensing portion of the detecting element will indicate the exact location of the fire.

A still further object of the invention is to provide a simplified fire detection system which will indicate when a fire has been extinguished as well as when a fire first exists in the structure.

These and other objects, features, and advantages will become more apparent after considering the following detailed description taken in conjunction with the annexed drawings and appended claims.

In the drawings wherein like reference characters refer to like parts in the views:

FIGURE 1 is a side view in partial section of the controlling mechanism for use in a system according to the present invention;

FIGURE 2 is a schematic diagram of the fire control system of the invention in use on an aircraft;

FIGURE 3 is a detail top view in partial section of the clevis attachment to the bimetallic strip; and

FIGURE 4 is a side elevation of the triangular way showing the steel ball disposed therein along the line 44 of FIGURE 1.

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Referring now to the drawings the controlling mechanism as shown in FIGURE 1 is illustrated in the form of a temperature sensing device 13 which includes a base plate 15 having attached thereto the angle support member 17. A strip of laminated bimetallic material 19 is fixedly attached to the support member 17 and extends upwardly from the base plate 15. The strip 19 is made by laminating two different metals having dissimilar thermal coefiicients of expansion which gives the strip the property of becoming deformed from the original straight form as illustrated to a bowed or warped configuration on being exposed to temperature changes. In the embodiment shown, the more thermally expansible material 21, such as silver, is disposed toward the outside while the less thermally expansible material 23, such as copper, is placed toward the inside.

Near the upper portion of the bimetallic strip 19, there is attached a pivotable clevis 25, more clearly shown in FIGURE 3. The clevis 25 pivots about a pin member 27 which passes through a hole in the bimetallic strip 19. One end of a rod 29 is fixedly attached to the clevis 25 and the other end of the rod 29 has a ball 31 attached thereto. It can be seen that any bowing or warping of the bimetallic strip 19 will cause corresponding movement of the rod 29 and the ball 31 attached thereto.

The ball 31 is disposed in the triangular way 33 which restricts its movement to the horizontal direction only and prevents vertical movement. The way 33, an end view of which is shown in FIGURE 4, is attached to the upper surface of the bracket member 35 which is permanently aflixed to the base plate 15 by means such as epoxy cement. A switch 37 is attached to the lower surface of the upper portion of the bracket 35. The button portion 39 of the switch 37 extends upwardly through aligned openings in the bracket 35 and the triangular way 33 and extends into the interior thereof. Thus it is apparent that as the ball 31 moves along the Way 33, the button portion 39 of the switch 37 becomes depressed by the ball 31 causing the normally open switch 37 to close. This initiates the flow of current through the wires 41 which are covered with asbestos to prevent damage due to excessive heat. A protective sheet metal cover 43 having a plurality of punched openings 45 for allowing heat to impinge on the bimetallic strip 19 is positioned over the temperature sensing device 13.

A typical aircraft fire detection system according to the invention is shown schematically in FIGURE 2. The temperature sensing devices 13 are mounted in the engine compartments which are numbered 1, 2, 3 and 4. Correspondingly numbered indicator lights 47 are connected thereto and operate when the current flowing through the wires 41 energizes the relay coils 49 which close the relay points 51 allowing current to flow to the indicator lights 47. As mentioned above, current flows through the wires 41 when a rapid ambient temperature rise occurs and the switch 37 is closed by the action of the bimetallic strip 19 causing movement of the steel ball 31. While only four temperature sensing devices 13 have been shown in the fire detection system, it will be under stood that any number may be utilized depending on nature and size of the area to be protected. Also, each area could be equipped with a plurality of sensing elements 13. For example, several units could be mounted and connected in parallel in each of the engines of a multiple engine aircraft with a single indicator light for each engine to show fire on that particular engine. This arrangement could also be utilized in stowage areas of the aircraft.

In the practice of the invention, the thermal sensing device 13 is installed in a remote area which may be vulnerable to fire or overheating. If a rapid ambient temperature rise occurs, the heat therefrom passes through the openings 45 in the cover 43 and impinges on the bimetallic strip 19. This causes the strip 19 to become deformed and bend into a bowed configuration. When this happens a rod 29 pivotally attached to the upper end of the bimetallic strip 19 moves in a substantially horizontal direction. A ball 31, disposed in the triangular way 33 and attached to the other end of the rod 29, moves in the way 33 an amount corresponding to the deformation of the bimetallic strip 19. A switch 37 with a button portion 39 extending upwardly into the triangular way 33 is closed when the ball 31 passes over it causing current to flow through the wires 41. This energizes the relay coils 49 causing the relay points 51 to close and light the indicator lights 47. Thus, any rapid temperature rise in the area of the sensing element 13 registers immediately in the indicator lights 47. When the temperature returns to normal, which would happen in the case of fire after the fire was extinguished, the ball 31 pulls away from the switch button 39 as a result of the bimetallic strip 19 returning to its normal configuration. This opens the switch 37 and turns oil the indicator lights 47 to signify that the fire is out.

The fire detection system according to the invention provides a simplified and dependable means for indicating the existence of a fire as well as its exact location. The sensing elements 13 may be placed in any position in various remote areas which are to be protected against fire. A single sensing element or a plurality may be incorporated in the detection system depending upon the size and particular conditions in the area to be protected.

Although the invention has been illustrated and described in terms of a preferred embodiment thereof, it will be apparent to one skilled in the art that certain changes, alterations, modifications, and substitutions can be made in the arrangement and location of the various elements without departing from the spirit and scope of the appended claims.

Having thus set forth and described the nature of my invention what I claim is:

1. A fire detection system for indicating a rapid ambient temperature rise in a remote area, said system including a temperature sensing device located in the area to be protected, said temperature sensing device comprising a fiat base member, an upstanding bimetallic strip having one end fixedly attached to said base member, said bimetallic strip adapted to bend in response to temperature changes, a rod having one end pivotably attached near the other end of said bimetallic strip and extending substantially horizontally therefrom, a ball affixed to the other end of said rod and movable in response to changes in configuration of said bimetallic strip, means for guiding said ball along a predetermined path, a switch having a button portion extending into said guide means in the path of said ball, electrical means connected to said switch and activated by the closing of said switch by said ball, and indicating means energized by said electrical means to show when said switch is closed by said ball in response to the movement of said bimetallic strip as the temperature in the area of said sensing device rises above a predetermined level.

2. The fire detection system defined in claim 1 wherein the means for guiding the movable ball of the temperature sensing device comprises an elongated triangular way aflixed to a bracket member, said triangular way being disposed in substantially parallel relationship to said rod and dimensioned to allow lateral movement and restrict vertical movement of said ball.

3. The fire detection system defined in claim 1 wherein the electrical means activated by the closing of said switch includes a relay having a magnetic coil energized by said electrical means, and a pair of contact points which close When said magnetic coil is energized, the closing of said contact points causing current to flow to said indicating means.

4. The fire detection system defined in claim 1 wherein the bimetallic strip adapted to bend in response to temperature changes comprises two different strips of metals bonded together, one of the strips being silver and the other strip being copper, the silver strip having the higher coefiicient of expansion being disposed away from the direction in which the bimetallic strip is to bend in response to a temperature rise so that the increased heat will cause more rapid expansion of the silver portion of the bimetallic strip and result in a bending of the bimetallic strip in the direction of the copper portion thereof.

References Cited UNITED STATES PATENTS 1,542,096 6/1925 Riblet.

JOHN W. CALDWELL, Primary Examiner. D. L. TRAFTON, Assistant Examiner. 

1. A FIRE DETECTION SYSTEM FOR INDICATING A RAPID AMBIENT TEMPERATURE RISE IN A REMOTE AREA, SAID SYSTEM INCLUDING A TEMPERATURE SENSING DEVICE LOCATED IN THE AREA TO BE PROTECTED, SAID TEMPERATURE SENSING SEVICE COMPRISING A FLAT BASE MEMBER, AN UPSTANDING BIMETALLIC STRIP HAVING ONE END FIXEDLY ATTACHED TO SAID BASE MEMBER, SAID BIMETALLIC STRIP ADAPTED TO BEND IN RESPONSE TO TEMPERATURE CHANGES, A ROD HAVING ONE END PIVOTALLY ATTACHED NEAR THE OTHER END OF SAID BIMETALLIC STRIP AND EXTENDING SUBSTANTIALLY HORIZONTALLY THEREFROM, A BALL AFFIXED TO THE OTHER END OF SAID ROD AND MOVABLE IN RESPONSE TO CHANGES IN CONFIGUTATION OF SAID BIMETALLIC STRIP, MEANS FOR GUIDING SAID BALL ALONG A PREDETERMINED PATH, A SWITCH HAVING A BUTTON PORTION EXTENDING INTO SAID GUIDE MEANS IN THE PATH OF SAID BALL, ELECTRICAL MEANS CONNECTED TO SAID SWITCH AND ACTIVATED BY THE CLOSING OF SAID SWITCH HAVING BALL, AND INDICATING MEANS ENERGIZED BY SAID ELECTRICAL MEANS TO SHOW WHEN SAID SWITCH IS CLOSED BY SAID BALL IN RESPONSE TO THE MOVEMENT OF SAID BIMETALLIC STRIP AS THE TEMPERATURE IN THE AREA OF SAID SENSING DEVICE RISES ABOVE A PREDETERMINED LEVEL, 